WesWorld

I'll post it here as well.

Whenever I try to sim a submarine, I always get the impression that with using the miscellaneous weight for the ballast, the ballast is somewhere above the water while the sub is just under the water. That does seem rather ridiculous. Stability does seem to be a bit of a problem especially if we're going to use the 0.65 additional weight rule for diesel/electric drive.
Now using Springsharp, I've been looking at a different way, but I'm not sure if it would be a correct way to sim a submarine (as a lot of people were rather sceptical about my trick to switch the mains and secondaries around to get superfiring secondaries when no superfiring mains were present, I thought I just post this before using it).

I used a Sub with ballast 1/5 of the normal displacement (1646 / 5 = 329.2 tons), used the 1.65 modifier for the diesel/electric drive as it has been discussed somewhere here in the Meeting Place (giving an engine weight of 195 tons * 1.65 = 321.75 tons) and used 1.3 tons for a torpedo (26 / 1.3 tons = 20 torpedoes).

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I-8, Japan Patrol Submarine laid down 1926

Displacement (submerged):
1,408 t light; 1,445 t standard; 1,646 t normal; 1,800 t full load
Loading submergence 111 tons/feet

Dimensions:
240.00 ft x 30.00 ft x 20.00 ft (normal load)
73.15 m x 9.14 m x 6.10 m

Armament:
1 - 4.13" / 105 mm guns
2 - 1.57" / 40 mm AA guns
Weight of broadside 39 lbs / 18 kg
7 - 21.0" / 533.4 mm submerged torpedo tubes

Armour:
Belt 7.66" / 195 mm, end belts 1.25" / 32 mm
Belts cover 100 % of normal area
Main belt does not fully protect magazines and engineering spaces

Machinery:
Diesel Internal combustion engines plus batteries,
Electric cruising motors plus geared drives, 1 shaft, 10,061 shp / 7,506 Kw = 22.63 kts
Range 7,000nm at 12.00 kts

Complement:
129 - 167

Cost:
£0.340 million / $1.361 million

Distribution of weights at normal displacement:
Armament: 5 tons, 0.3 %
Armour: 355 tons, 21.6 %
Belts: 355 tons, 21.6 %, Armament: 0 tons, 0.0 %, Armour Deck: 0 tons, 0.0 %
Conning Tower: 0 tons, 0.0 %, Torpedo bulkhead: 0 tons, 0.0 %
Machinery: 322 tons, 19.6 %
Hull, fittings & equipment: 726 tons, 44.1 %
Fuel, ammunition & stores: 237 tons, 14.4 %
Miscellaneous weights: 0 tons, 0.0 %

Metacentric height 1.4

Remarks:
Hull space for machinery, storage & compartmentation is cramped
Room for accommodation & workspaces is extremely poor
Ship has quick, lively roll, not a steady gun platform
Caution: Lacks seaworthiness - very limited seakeeping ability

Estimated overall survivability and seakeeping ability:
Relative margin of stability: 1.33
Shellfire needed to sink: 744 lbs / 338 Kg = 21.1 x 4.1 " / 105 mm shells
(Approx weight of penetrating shell hits needed to sink ship excluding critical hits)
Torpedoes needed to sink: 0.3
(Approx number of typical torpedo hits needed to sink ship)
Relative steadiness as gun platform: 0 %
(Average = 50 %)
Relative rocking effect from firing to beam: 0.00
Relative quality as seaboat: 0.00

Hull form characteristics:
Block coefficient: 0.400
Sharpness coefficient: 0.32
Hull speed coefficient 'M': 6.21
'Natural speed' for length: 15.49 kts
Power going to wave formation at top speed: 59 %
Trim: 50
(Maximise stabilty/flotation = 0, Maximise steadiness/seakeeping = 100)

Estimated hull characteristics & strength:
Underwater volume absorbed by magazines and engineering spaces: 112.9 %
Relative accommodation and working space: 0.0 %
(Average = 100%)
Displacement factor: 158 %
(Displacement relative to loading factors)
Relative cross-sectional hull strength: 2.46
(Structure weight / hull surface area: 109 lbs / square foot or 532 Kg / square metre)
Relative longitudinal hull strength: 2.47
(for 0.00 ft / 0.00 m average freeboard, freeboard adjustment -10.56 ft)
Relative composite hull strength: 2.46

Normal depth: 246 feet
Emergency depth: 369 feet
Crush depth: 615 feet

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Now the 7.66 inch belt at 100% coverage gives me 330 tons and this is located lower in the ship than the miscellaneous weight (which is located somewhere above the waterline). Also if I somewhat adjust the dimensions of the sub, the tonnages assigned to the belt also change, and if you do not change the ship too much, will stick reasonably close to the 1/5 of the normal displacement.
The 1.25 inch end belts give me 26 tons at the points where one would store the torpedoes.


Using the old way would give you this:

==============================================
I-8, Japan Patrol Submarine laid down 1926

Displacement:
1,408 t light; 1,445 t standard; 1,646 t normal; 1,800 t full load
Loading submergence 111 tons/feet

Dimensions:
240.00 ft x 30.00 ft x 20.00 ft (normal load)
73.15 m x 9.14 m x 6.10 m

Armament:
1 - 4.13" / 105 mm guns
2 - 1.57" / 40 mm AA guns
Weight of broadside 39 lbs / 18 kg
7 - 21.0" / 533.4 mm submerged torpedo tubes

Machinery:
Diesel Internal combustion engines plus batteries,
Electric cruising motors plus geared drives, 1 shaft, 6,102 shp / 4,552 Kw = 20.00 kts
Range 7,000nm at 12.00 kts

Complement:
129 - 167

Cost:
£0.279 million / $1.116 million

Distribution of weights at normal displacement:
Armament: 5 tons, 0.3 %
Machinery: 195 tons, 11.9 %
Hull, fittings & equipment: 725 tons, 44.1 %
Fuel, ammunition & stores: 237 tons, 14.4 %
Miscellaneous weights: 483 tons, 29.3 %
(ballast: 330 tons, diesel/electric drive: 127 tons, torpedoes 26 tons)
Metacentric height 0.6

Remarks:
Caution: Poor stability - excessive risk of capsizing
Hull space for machinery, storage & compartmentation is cramped
Room for accommodation & workspaces is extremely poor
Ship has quick, lively roll, not a steady gun platform
Caution: Lacks seaworthiness - very limited seakeeping ability

Estimated overall survivability and seakeeping ability:
Relative margin of stability: 0.86
Shellfire needed to sink: 294 lbs / 133 Kg = 8.3 x 4.1 " / 105 mm shells
(Approx weight of penetrating shell hits needed to sink ship excluding critical hits)
Torpedoes needed to sink: 0.1
(Approx number of typical torpedo hits needed to sink ship)
Relative steadiness as gun platform: 0 %
(Average = 50 %)
Relative rocking effect from firing to beam: 0.00
Relative quality as seaboat: 0.00

Hull form characteristics:
Block coefficient: 0.400
Sharpness coefficient: 0.32
Hull speed coefficient 'M': 6.21
'Natural speed' for length: 15.49 kts
Power going to wave formation at top speed: 53 %
Trim: 50
(Maximise stabilty/flotation = 0, Maximise steadiness/seakeeping = 100)

Estimated hull characteristics & strength:
Underwater volume absorbed by magazines and engineering spaces: 124.2 %
Relative accommodation and working space: 0.0 %
(Average = 100%)
Displacement factor: 180 %
(Displacement relative to loading factors)
Relative cross-sectional hull strength: 2.51
(Structure weight / hull surface area: 109 lbs / square foot or 531 Kg / square metre)
Relative longitudinal hull strength: 2.58
(for 0.00 ft / 0.00 m average freeboard, freeboard adjustment -10.56 ft)
Relative composite hull strength: 2.52
==============================================

Springstyle notes say that "Some nations' real subs had closer to 1/3, but this will not sim well." Main reason for that is that you have to deal with the stability dropping below 1.00 if you add too much miscellaneous weight. Using the belt as ballast does allow you to create such a submarine without the poor stability warning.

I'm no real expert so I would like to know from those who are: would this way work to sim a submarine?

Walter